1. Field of the Invention
This invention relates to a repairing material for bricks of a carbonizing chamber in a coke oven and a repairing method.
2. Description of the Prior Art
The carbonizing chamber in a coke oven is affected by various factors such as abrasion by the raw material coal, exposure to frequent repetition of cooling and heating cycles, and invasion by carbon. The surface of its bricks therefore sustain peeling and cracking, gradual excoriation of the consequently affected portions, and, eventually, heavily undulating contouring. The refractory bricks which surround the cast iron frame located near the mouth of the oven are particularly susceptible to peeling and cracking and experience severe surface degradation owing to such mechanical factors as the shocks caused by the opening and closing of the oven lid. Since this degrades the airtightness of the carbonizing chamber, it forms a cause for gas leakage and poses a serious problem regarding the quality of the produced coke and the production efficiency.
One approach to this problem is to repair commercial coke ovens by blowing a powder refractory into the broken portions of joints between adjacent bricks or into the fractured portions of the bricks. For example, Japanese Patent Publication Sho 55-46998 teaches a composition using mortar as a main component and incorporating therein a bituminous substance and a liquid oil, Japanese Patent Publication Sho 56-5713 teaches a composition using a basic refractory aggregate (such as magnesia clinker) as a main component and incorporating therein a lithium compound, clay, and sodium silicate, and Japanese Patent Publication Sho 56-15763 teaches a method for effecting repair by using a dry blowing device to hot-blow a powder refractory containing magnesia clinker, for example, as a main component. The repairing materials of these inventions are intended to be used either dry or wet. The methods involved in these inventions invariably rely on the use of a gun or a nozzle to apply a repairing material fed from a pressure tank to the oven wall. In reality, however, inexpensive mortar or a repairing material containing mortar as a main component is used most widely in the repair of coke oven carbonizing chamber bricks.
However, such conventional repairing materials basically exhibit only poor adhesive property to cast iron and bricks (refractory). Since this makes them readily susceptible to peeling and cracking owing to the various factors mentioned above, they fall off the surface of the cast iron and the surface of bricks. The repair with these repairing materials therefore quickly loses its effect and the repair work must be frequently repeated.
The life of the repair work is especially short when the blown repairing material happens to contain much water because the applied layer of the wet repairing material emits steam while drying and the pressure of this steam easily separates the applied layer of the repairing material from the oven wall and the bubbles produced in consequence of the evaporation of the substance having a low melting points easily give rise to cavities which cause cracks in the applied layer.
In the case of the mortar spray which is in popular use, for example, since the mortar has a proper particle size distribution in the approximate range of 0.05 mm--several mm and uses SiO.sub.2 and Al.sub.2 O.sub.3 as main components, the applied layer of this repairing material does not conspicuously give rise to cavities in consequence of the formation of bubbles. The life of the repair work by the mortar spray, however, is only about one week because the mortar exhibits an extremely weak adhesive power to cast iron and bricks.
When the repairing material which contains mortar as a main component as described above is used for repair, the adhesive property is somewhat better than that of the repairing material which is formed solely of mortar. When the solidified applied layer of this repairing material is exposed to repeated cooling and heating cycles, however, it ultimately sustains cracks owing to the repeated cycles of contraction and expansion. When this happens, the tarry matter in the oven enters the cracks and coagulates in the cracks when the applied layer cools. Repetition of this process gradually enlarges the cracks and promotes separation of the applied layer of repairing material from the oven wall.
None of the existing repairing materials using mortar as a main component is found to be capable of providing a lasting repair effect.